Know Your Rights

It is 100% legal to openly record police in all 50 states as long as you do not physically interfere with the officer. (It's also probably wise to speak as little as possible, but DO make note of details - location, names, etc)

Police officers do not have a "reasonable expectation of privacy" while preforming their public duties.

If an officer says it's illegal to record him, that officer is lying to try and trick you into shutting off the camera so you won't have proof of them violating your rights.

Use a livestreaming app to record your videos. If your phone is seized, the police cannot delete the video because the video was never on the phone to begin with.